Co-cure of blend of rubber of low unsaturation and highly unsaturated rubber using long chain hydrocarbon dithiocarbamate accelerators

ABSTRACT

Use of such long chain hydrocarbon dithiocarbamate accelerators as zinc N-dodecyl, N-isopropyl dithiocarbamate in the sulfur cure of blends of rubber of low unsaturation, particularly EPDM, with highly unsaturated rubbers such as SBR, NBR, etc., produces vulcanizates having high tensile strength.

nited States Patent Mastromatteo et a1.

Thomas J. Brett, Jr., Cheshire, both of Conn.

Uniroyal, Inc., New York, NY.

Sept. 9, 1970 Inventors:

Assignee:

Filed:

Appl. No.:

[52] U.S. Cl ..260/889, 152/330, 161/253, 260/23 H, 260/23.7 M, 260/23.7N, 260/23.7 R, 260/28.5 B, 260/33.6 AQ, 260/41 R, 260/41 A, 260/41 B,260/41.5 R, 260/9l.5 A, 260/79.5 P, 260/79.S B, 260/429 K, 260/429.9

Int. Cl. ..C08f 29/12 Field of Search ..260/889, 79.5 P, 79.5 B, 429.9,260/429 K 15 3,678,135 [4 1 July 18, 1972 [56] References Cited UNITEDSTATES PATENTS 3,331,793 7/1967 Soufile ..260/4 OTHER PUBLICATIONSHofmann, vulcanization and Vul. Agents, pp. 106- 111 July 68 PrimaryExaminer-Samuel l-l Blech Assistant Examiner-C. J. SeccuroAttorney-James J Long [57] ABSTRACT Use of such long chain hydrocarbondithiocarbamate accelerators as zinc N-dodecyl, N-isopropyldithiocarbamate in the sulfur cure of blends of rubber of lowunsaturation, particularly EPDM, with highly unsaturated rubbers such asSBR, NBR, etc., produces vulcanizates having high tensile strength.

23 Claims, No Drawings CO-CURE OF BLEND OF RUBBER OF LOW UNSATURATIONAND HIGHLY UNSATURATED RUBBER USING LONG CI-IAIN I-IYDROCARBONDITI-[IOCARBAMATE ACCELERATORS CROSS-REFERENCE TO RELATED APPLICATIONBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a vulcanizable rubber composition, a method of vulcanizing,and a vulcanizate so obtained.

2. Prior Art Blends of EPDM with highly unsaturated rubbers are known tohave desirable properties (e.g., U.S. Pat. Nos. 3,356,764, Dec. 5, 1967and 3,419,639, Dec. 31, 1968 of Gentile; also 3,443,619, May 13, 1969,Kindle), particularly from the standpoint of ozone resistance. However,because of the disparity of curing characteristics between the two kindsof rubber it has been difficult to obtain a good co-cure in the blend.Various special accelerating systems have been suggested (e.g., U.S.Pat. Nos. 3,343,582, Sept. 26, 1967, Himes et al. and 3,45 l ,962, June24, 1968, Auler et al.). The present invention employs acceleratorswhich result in high tensile strength in the blends.

SUMMARY OF THE INVENTION In accordance with the invention, the sulfurcure of a blend of a rubber of low unsaturation with a highlyunsaturated rubber is accelerated by using a long chain hydrocarbondithiocarbamate accelerator.

DETAILED DISCLOSURE The blend with which the invention is concernedcomprises a rubber of relatively low unsaturation, blended with a rubberof relatively high unsaturation.

Low unsaturation rubbers include butyl rubber and EPDM. EPDM may bedefined as a rubbery copolymer of two or more different alphamonoolefinswith at least one copolymerizable polyene. Usually two monoolefins areused, one of which is ordinarily ethylene and the other of which istypically propylene, but other pairs may be used, such asethylenebutene, propylene-pentene, etc., or more than two olefins may beused, as in ethylene-propylene-butene. The copolymerizable polyene,which confers unsaturation and sulfurvulcanizability on the copolymer,is ordinarily a diene, particularly a nonconjugated diene, whether openchain as in such straight or branched chain diolefins as 1,4-hexadiene,l,5-hexadiene, 1,9-octadecadiene, Z-methyll ,5-hexadiene, 6-methyll ,5-heptadiene, etc; or cyclic (particularly bridged ring) as indicyclopentadiene, methylene norbornene, ethylidene norbornene, propenylnorbornene, isopropylidene norbornene, butenyl norbornene, methyltetrahydroindene, etc. -Alkylidene- 2-norbornenes constitute animportant class. More than one diene may be employed. In typicalconventional EPDMs, the weight ratio of ethylene to propylene isfrequently within the range of from 20/80 to 80/20, preferably between30/70 and 70/30 by weight. The diene content is relatively low, usuallyfrom about 2 to 20 percent, preferably 4 to 12 percent, by weight of theterpolymer. Such amorphous, elastomeric copolymers are further describedin the patents referred to above, as well as U.S. Pat. Nos. 3,000,866;3,000,867; 2,933,480; 3,480,066 and 3,492,370. Preferred dienes aredicyclopentadiene, and 5-ethylidene-2-norbornene.

The rubber of relatively high unsaturation may be defined as aconjugated diene elastomer, whether a homopolymer as in such diolefinhomopolymers as polybutadiene (emulsionprepared or solution-prepared,whether of high cis content or otherwise), polyisoprene (natural orsynthetic, emulsionprepared, or solution-prepared, of high or low ciscontent), polychloroprene, etc., or copolymers of such diolefins asbutadiene or isoprene with copolymerizable monoethylenically unsaturatedmonomers such as styrene, acrylonitrile, vinyl pyridine, ethyl acrylate,methyl methacrylate or a mixture of such monomers. Usually the copolymercontains at least 50 percent by weight of the diolefrn. More than onesuch highly unsaturated rubber may be used in the blend (e.g., NR andSBR, NR and polyisoprene).

The ratio of rubber of low unsaturation to rubber of high unsaturationin the blend of the invention is usually in the range from 5:95 to 95:5,preferably 20:80 to :20, more preferably 30:70 to 70:30.

The composition of the invention is compounded for sulfurvulcanization,using as the accelerator a long chain hydrocarbon dithiocarbamate of theformula NJCLSlM where M is a metal (e.g., zinc, tellurium, nickel, iron,sodium, selenium, bismuth, copper, mercury, magnesium, lead, tin,cadmium, arsenic, antimony, etc., or, equivalently, ammonium), n is anumber equal to the valence of the metal and R and R are the hydrocarbonmoities. The hydrocarbon moieties R and R are non-aromatic and takentogether have a total number of at least 10 carbon atoms, preferably atleast 14 carbon atoms, and more preferably at least 18 carbon atoms. Atleast one of the hydrocarbons R, R has at least eight carbon atoms,preferably at least 12 carbon atoms. A preferred hydrocarbon group isalkyl, having for example up to 30 carbon atoms. One of the alkyls, R,R'may be a cycloalkyl (e.g., cyclopentyl, cyclohexyl) provided the otherhas at least eight carbon atoms. Of particular interest are the metaldialkyl dithiocarbamates of the foregoing kind which are unsymmetrical,that is, those having one relatively long chain alkyl (e.g., eight,preferably 12, to 20 or more carbon atoms) and one relatively shorterchain (e.g., three to six carbon atoms). Examples include zincN-dodecyl, N-isopropyl dithiocarbamate, ferric N-octyl, N-propyldithiocarbamate, selenium N- dodecyl, N-propyl dithiocarbamate, sodiumN-octadecyl, N- propyl dithiocarboamate, tellurium N-octyl, N-hexyl (orcyclohexyl) dithiocarbamate, nickel N-dodecyl, N-hexyl dithiocarbamate,copper N-octadecyl, N-hexyl dithiocarbamate, bismuth di(doceyl)dithiocarbamate, lead di(octadecyl) dithiocarbamate, magnesium N-n(mixedC C alkyl)-N- isopropyl dithiocarbamate, tin N-n-octadecyl-N-(1,3-dimethyl butyl) dithiocarbamate, cadmium N-n-octadecyl-N-isopropyldithiocarbamate, zinc N-n-octyl-N-isobutyl dithiocarbamate, etc.

These accelerators may be prepared in known manner by reaction of theappropriate amine with carbon disulfide. The amine used in makingN-dodecyl, N-isopropyl dithiocarbamate may be made by alkylation ofdodecylamine with acetone.

The accelerator is employed in conventional amounts and the compositionmay otherwise be compounded in accordance with conventional practice forsulfur vulcanization using sulfur itself or a conventionalsulfur-yielding curative, in conventional amounts.

Other conventional compounding ingredients may be present including suchactivators as metal oxides or salts, fillers or pigments such as carbonblack, silica, zinc oxide, extender oils, plasticizers, processing aids,lubricants, stabilizers, antioxidants, antiozonants, blowing agents,etc. The accelerators of the invention may also be used in combinationwith other conventionally known accelerators if so desired.

The mixture may be prepared in conventional mixing equipment such as aBanbury mixer or a roll mill according to standard practice, andvulcanized in a desired shape at elevated temperature under conventionalvulcanizing conditions appropriate to the particular article beingfabricated.

IOI045 0158 The vulcanizate prepared in accordance with the invention ischaracterized by improved physical properties, especially higher tensilestrength than is obtained when the same blend of rubbers in sulfur curedwith conventionally used accelerators, as distinguished from the longchain hydrocarbon accelerators described above. Such improved tensileproperties are belived to be evidence of co-cure of the rubbers of twodifferent degrees of unsaturation, or attainment of more or lessequivalent states of cure in the different rubbers.

A particularly useful embodiment of the invention relates to a sidewallfor a pneumatic tire, or a part ofa sidewall such as a cover strip orwhite sidewall, formulated for sulfur curing using the accelerator ofthe invention. Remarkable resistance to ozone and to cracking is anoutstanding characteristic of the present vulcanizates, which rendersthem particularly valuable for this purpose. The sidewalls or partsthereof display improved adhesion to parts of the tire to which they arevulcanized made of the usual highly unsaturated rubber compositions(e.g., NR, SBR, cis-polybutadiene, polyisoprene, or blends thereof).

The blends may be used in other applications; for example tire tread andcarcass compositions as well as compositions for hose, weatherstripping, sponge, wire and cable jacketing or insulation, belting, andthe like.

An important aspect of the invention resides in a laminate, in which alayer of the composition of the invention is disposed in face-to-facecontact with a layer of conventional rubber stock, the two layers beingvulcanized together with resulting good adhesion of the layers to eachother. The layer to which the composition of the invention is thusadhered is typically a highly unsaturated rubber stock as above definedand it may be compounded for sulfur vulcanization in the conventionalmanner, using a conventional accelerator, or, optionally, it may ifdesired employ the special long chain hydrocarbon dithiocaramateaccelerator of the same rubbers as ordinarily used in carcass and treadstocks. The parts may be fabricated by calendering or extrusion in theusual manner. Assembly of the parts in the usual manner, for examplewith the aid ofa tire building drum, followed by shaping andvulcanization in a tire curing mold, results in a finished pneumatictire in which the sidewall composition of the invention has goodphysical properties, is ozone-resistant, and adheres firmly to thecarcass, even when the tire develops elevated internal temperaturesunder conditions of severe or high speed usage. if desired, thespecially accelerated blend of the invention may also be used for otherparts of the tire as well, particularly the tread or carcass.

The following examples will serve to illustrate the practice of theinvention in more detail.

EXAMPLE 1 The materials shown in Table 1 are blended together, in theamounts shown in the table, to make nine different stocks having variouscompositions. The stocks identified as 1-1 represents the invention;stocks l-A to 1-H are included for comparison. The EPDM employed is anethylene-propylene- 5-ethylidene-2-norbornene terpolymer containing 43percent propylene by weight, iodine number 20, Mooney viscosity 75 (ML-4at 212F). The highly unsaturated rubber employed is a styrenebutadienecopolymer rubber, SBR 1502, containing about 23 percent styrene. Theextender oil is Circosol 4240. The accelerators are employed atequivalent molecular quantities (i.e., 0.00164 moles 100 g of blend).The stocks are cured in a mold at 320F for 20 minutes and 30 minutes,and the physical properties are determined, with the results shown inthe table. The tensile properties of the blended rubbers cured using theaccelerator of the invention, namely zincdodecylisopropyl-dithiocarbamate, stock 1-1, are far superior to thetensile properties of blends made with conventional accelerators, stocksI- C and l-F.

[Comparison of long chain hydrocarbon dithiocarbamate accolieriggg1611]) short chain dithiocarbamate accelerators in blends of 8BR Curetime

Carbon Black. Extender Oil Zinc Oxide.. Stearic Acid- Zinc dimethy Zincdibutyldithiocarbamate.

Zinc dodecylisopropyldlthioearbamate 6 Sulfur 2. 5 Physical propertiesafter cure at 320 F.: 20 1 020 1 400 790 l 000 700 990 1 410 so: 1: 22011 2 11%;; 1 388 1: 188 IIIII I I I 980 1,190 1:600 20 2, 200 2, 1, 1, 11, 750 1, 9110 1, 610 T611511 Strength so ,300 2, 1, 3 8g 2, 1, 323 1,2, 180 2,150 1,680 20 650 25 780 640 390 Elmgatlmh Percent character asemployed in the EPDM-highly unsaturated blend EXAMPLE ll of theinvention.

The stock of the invention may be used as a tie gum, or may be appliedas a cement, to adhere two other vulcanizable The stocks shown in Table11 are prepared using the same layers together.

A preferred specific embodiment of the invention is a pneumatic tireconstructed in the usual manner with a filamentreinforced carcass(reinforced with strands of organic textile, glass, or steel) on whichis superimposed the usual tread as the road-contacting member, and whichhas applied to its sides sidewall members. In accordance with theinvention at least a portion of the tire, particularly the sidewall or aportion thereof, especially a white sidewall and if desired a blackcoverstrip, is made of the EPDM highly unsaturated rubber blend of theinvention containing the described special accelerator. Examples ofsuitable white sidewall and coverstrip stock formulations are set forthin the working examples below. The carcass and tread may be compoundedconventionally of the usual vulcanizable highly unsaturated rubber orEPDM as in Example 1, but using a butadiene-acrylonitrile copolymerrubber (Paracil BLT, containing 32 percent acrylonitrile) as the highlyunsaturated rubber. Stock ll-F represents the invention; stocks lI-A toll-E are included for comparison. MBTS" (2,2'-benzothiazyl disulfide) isused in controls ll-A to Il-C because a zinc dimethyldithiocarbamatecure alone is much too scorchy to handle in NBR. The dithiocarbamateaccelerator concentration is 0.00328 moles/100 g of the blend in allcases. After curing at 320F for the times shown in Table 11, theproperties are determined, with the results shown. The superiority ofstock ll-F of the invention over the control blend ll-C is manifest. Theexample may be repeated, using as the EPDM anethylene-propylenedicyclopentadiene terpolymer containing 35 percentpropylene by weight, iodine number 13, Mooney viscosity ML-4 at 212F.The example may be repeated, using the vari- Stocks iV-D, lV-E, and iV-Fthe concentration is 0.00164. ous accelerators of the invention namedpreviously. Th EPDM i m same as i E l TABLE II [Comparison of long chainhydrocarbon dithiocarbamato accelerators to short chain dithiocnrbamutoaccelerator in NB R/EPDM blends] Cure II-A II-B NB R 100. EPDM 100.0Zinc oxide 5.0 5.0 Carbon black. 50. 0 50. 0 0. 76 0. 75 3. 0 3.0 1.0 1. 0 Zinc dodccylisopropyldithiocarbam Sulfur 1.0 l. 0 Physicalproperties:

Cure 1, minutes at 320 F 10 Cum 2, minutes at 320 F 15 300% modulus,p.s.i iggg g'gg Tensile strength, p.s.i $33 g 33% Elongation, percentHardness, A

[Comparison of long chain hydrocarbon dithiocarbamate accelerators toshort chain dithiocarbamate accelerators .1. @BJEB M P f i,

EXAMPLE III TABLE IV In Table III, a white sidewall composition of theinvention containing zinc dodecylisopropyl dithiocarbamate (StockDecyhsopmpyldthmcarbamme Ill-B) is compared to one containing theconventional zinc Dodecylisopropyldithiocarbamatedimethyl-dithiocarbamate accelerator. The EPDM contains ethylene andpropylene in 65/35 weight ratio, and 5 percent and b weight ofdicyclopentadiene. The zinc oxide is XX203. The

siiisa filler is l-li Si] 215. The titanium dioxide is Titanox RA. 35omdmyhmPmPY'dmmabamae The oil is naphthenic Circo light oil. The wax isa rnicrocrystalin an line paraffin wax blend, Sunproof Improved. Theaccelerator concentration in both cases is 0.00136 mole per 100 g ofSBR/EPDM Blend rubber. The stocks are compounded in a Banbury typeinter- 40 nal mixer in the conventional manner at a temperature notexceeding 320'F. The accelerator is added to the stock on a rubber millat about SBR 1502 50.0 50.0 50.0 50.0 50.0 50.0 EPDM 50.0 50.0 50.0 50.050.0 50.0 TABLEIII N-550 Black 80.0 80.0 80.0 80.0 80.0 80.0 Zinc Oxidev 5.0 5.0 5.0 5.0 5.0 5.0 white sidewallsmcks Stearic Acid 0.75 0.750.75 0.75 0.75 0.75

' Y Circosol 4240 50.0 50.0 50.0 50.0 50.0 50.0 lll-A ill-B Zinc smakedsheets I I 50 50 dirnethylthiocarbamate 1.0 0.5 EPDM 2 5 25 Zincdecylisopropyl- SBR 502 25 25 dithiocarbamate 2.0 Zinc oxide 20 20 Zincdodecyhsopropyl- Silica filler 15 15 dlthlocarbarnate 2.2 l.i Titaniumdioxide as 35 g gp y v gl 4 St 2 2 py 1 iocar ama e 31133 oil 5 5 Sulfur2.5 2.5 2.5 2.5 2.5 2.5 Wax 5 5 Zinc dimethyl-dithiocarbamate 0.45Mooney Scorch at 70 '45 1 2'00" Zinc dodecylisopropyl-dithiocarbamate'1.0 l3'30"l1'15" 18'00" 1715" Sulfur 2.0 2.0 Mooney scorch at 270F ll15'' 15' 30" Physical Properties, Cured at 320F 20' 1900 1410 1430 ii izgii cums g o' u 1600 1590 300% Modulus 210 300 Tensile su'ength, psi.1040 i380 Elon ation 820 740 20 1300 1600 1920 1250 1610 1610 flardgessA 47 so 30' 1300 1780 1830 1280 1680 1500 Elongation 10' 210 300 380 20160 250 300 250 390 360 EXAMPLE IV 30' 160 260 270 230 340 300 a eustrates e practice 0 the invention with an shore A 66 61 60 EPDM-SBRblend, accelerated with decylisopropyl-dithiocar- 20' 67 63 62 63 63 64bamate (Stocks lV-B), docecylisopropyl-dithiocarbamate 68 64 64 64 63 67(Stock lV-C, lV-E) and octadecylisopropyldithiocarbamate EXAMPLEV (StocklV-F). in stocks IV-A, IV-B and lV-C the concentration of accelerator is000328 mole per 100 g of rubber; in In the blends of Table V, EPDM-l hasan 189 101045 (llfin ethylene/propylene ratio of 57/43; iodine number10; the diene is 5-ethylidene-2-norbomene; the Mooney viscosity is 55(ML-4 at 212F). EPDM-2 is the same as the EPDM of Example Theaccelerator concentration is 0.00164 mole per 100 g of rubber.

TABLE V Long Chain Hydrocarbon Dithiocarbamates in a NBR/EPDM Blend V-AV-B V-C V-D V-E V-F PARACRIL BLT 50.0 50.0 50.0 50.0 50.0 50.0 EPDM-l50.0 50.0 50.0 EPDM-2 50.0 50.0 50.0 N-774 Black 50.0 50.0 50.0 50.050.0 50.0 Zinc Oxide 5.0 5.0 5.0 5.0 5.0 5.0 Stearic Acid 0.75 0.75 0.750.75 0.75 0.75 Zinc dimethyldithiocarbamate 0.5 0.5 Zincdodecylisopropyldithiocarbamate l l l .l Zincoctadecylisopropyldithiocarbamate l .4 l .4 ur 2.0 2 0 2.0 2.0 2.0 2.0

Physical Properties, Cured 30' at 320F Tensile strength, psi 650 13901820 650 1500 1850 Elongation, 130 230 260 140 200 260 Hardness, Shore A70 69 70 70 70 70 EXAMPLE VI Table V1 shows blends of the EPDM ofExample 1 with polychloroprene rubber (Neoprene W). The oil used is anaromatic extender oil, Sundex 790. The accelerator concentration is0.00328 mole per 100 g of rubber.

TABLE VI Long Chain Hydrocarbon Dithiocarbamates in aPolychloroprene/EPDM Blend EXAMPLE V11 In Table VII, stocks VII-A andVII-B are carcass stocks (CAR), stocks Vll-C and Vll-D are whitesidewall stocks (WSW), and stocks Vll-E and Vll-F are coverstrip stocks(CS). in this series, adhesion comparisons are made between l.Standard-cured black stock with standard-cured black EPDM Blend (A-E).2. Specially-cured black stock with invention-cured black EPDM Blend(B-F). 3. Standard-cured WSW EPDM blend with standard-cured black EPDMblend (C-E). 4. Invention-cured black EPDM blend with invention-curedWSW EPDM blend F-D). The EPDM employed in Table VII is the same as inExample 111. The wax used is Sunproof Improved. Circosal 4240 naphthenicextender oil. Octamine is octylated diphenylamine. Theresorcinol-aldehyde resin may be as described in U.S. Pat. No.3,256,137, Danielson, June 14, 1966, col. 6, lines 8-12. The adhesiveagent is 1-aza-5-methy1o1-3,7-dioxabicyclo [3.3.0] octane. Delac-S isN-cyclohexyl-Z- benzothiazole sulfenamide. Delac MOR is N-oxydiethylenebenzothiazole-2-sulfenamide. DPG is diphenylguanidine.

The adhesion tests results given in Table VII were determined by theprocedure of ASTM-D-4 l 3. The results demonstrate the ability of EPDMblends, accelerated in accordance with the invention, whether whitesidewall stock or black coverstrip stock, to adhere to highlyunsaturated rubber stock such as carcass stock (cured conventionally, orcured with the accelerator used in the invention). In these tests, theindicated stocks are placed in face-to-face contact to make a laminate,placed in a mold and cured to vulcanize the stocks to each other, andthen the adhesion test is carried out on the cured laminates. 1n thetable 1nt." indicates an interfacial separation, St." indicates that thestock tore with no adhesion failure.

TABLE VI] Adhesion of coverstrip Carcass and White Sidewall V11 V11 V11V11 V11 V11 A -B -C -D -E -1- CAR CAR WSWWSWCS CS Smoked Sheets 40.040.0 50.0 50.0 40.0 40.0 SBR 1715 90.0 90.0 EPDM 25.0 25.0 30.0 30.0 SBR1502 25.0 25.0 30.0 30.0 N-550 Black 60.0 60.0 25.0 25.0 XX 203 ZincOxide 3.5 3.5 20.0 20.0 3.5 3.5 Hi Si] 215 15.0 15.0 Titanox RA 35.035.0 Stearic Acid 1.5 1.5 2.0 2.0 2.0 2.0 Circo Lt. Oil 5.0 5.0 3.0 3.0Wax 5.0 5.0 Circosol 4240 5.0 5.0 0C1 AMINE 1.0 1.0 Resorcinol-aldehyderesin 2.0 2.0 Adhesive agent 1.0 1.0 DELAC S 1.0 MBTS 1.25 DELAC MOR 1.0DPG 0.2 0.3 0.3 0.3 Zinc dodecylisopropyldithiocorbamaste 0.75 0.75 0.75Sulfur 3.25 3.25 2.5 2.5 2.0 2.0

Static Adhesion at 250F, after Laminating and Curing Stocks in ExampleVII, are given in Table V111, wherein the EPDM is the same as in Exampleill. The cis-BR is Cis-4 No. [203" of Phillips Petroleum, about 95percent cis content. Paraflux is a hydrocarbon resin.- The antiozonantmay be N-phenyl-N- hexyl-p-phenylene diamine. In order to observe theimproved adhesion according to the invention the following pairs may becompared in Table VIII:

A-B to A-C (=std. v. invention) Ill The secondary amines used in thesepreparations may be prepared by.reductive alkylation of primary amineswith ketones.

Having thus described our invention, what we claim and desire to protectby Letters Patent is:

l. A composition comprising a blend of (A) 5 to 95 parts by weight of anethylene-propylene-non-conjugated diene terto polymer rubber containingethylene and propylene in weight 84) to ratio of from /80 to 80/20 andfrom 2 to 20 percent by to 10 weight of said non-conjugated diene, and(B) correspondingly TABLE VIII [Use of long chain hydrocarbondithioearbamates for improved adhesion] VIII-A VIII-B VIII-C VIII-DVIII-E VIII-F VIII-G Smoked sheets 40. 0 0

SBR 1712 oz-.. 68.76 68.75 40 0 n Sunproof imp- XX 203 zinc oxide Hi Sil215 oolllllll Zinc dodecyllsopropyl dithlocarbamate l. 0 1. 0 Sulfur3.25 2.2 2.0 2 0 2.0 2.5 Stock to stock adhesion A-B A-C A-D A-E B-D B-ED-F D-G Adhesion at 250 F.-

Lbs. p 42 50 8.0 29 16 40 17v 67 Type Failure.. Stock Stock Int. StockInt. Stock Int. Stock stock stock Zinc dodecylisopropyl dithiocarbamatemay be prepared as follows: in a 2-liter, three-neck, round-bottom flaskequipped with a stirrer, thermometer and dropping funnel is placed 60'grams [.5 moles) of sodium hydroxide and 60 ml of water (or 120 grams of50 percent sodium hydroxide solution). One thousand ml. of isopropanoland 341 gm. (1.5 moles) of N-ndodecyl-N-isopropyl amine. To this stirredsolution is added I26 gm. (1.66 moles, 100 ml.) of carbon disulfide atsuch a rate as to maintain the reaction temperature at 25 -35 C. Afterall of the carbon disulfide has been added the solution is poured into arapidly stirring solution of 140 gm. of zinc sulfate in L000 ml. ofwater. The rapid stirring is continued until the zinc salt solidifies(rapid stirring is important, and will cause small particle sizesolidification of the zinc salt and prevents caking of the mixture thusentrapping impurities). This gives a compound with an easilyfilterableparticle size. When the product solidifies it is removed by filtrationand dried. The yield is 98 percent of a white solid, m.p. 84-85C.

The following dithiocarbamic acid zinc salts may be made by an analogousprocedure to that above by substitution of the appropriate amine forN-n-dodecyl-N-isopropyl amine:

The mixed C -C alkyl amines are a tallow amine product commerciallyavailable as Armeen HT from to 5 parts by weight of a conjugateddiolefin polymer rubber containing at least 50 percent by weight of saidconjugated diolefin, said blend containing sulfur as a vulcanizing agentand, as an accelerator of sulfur vulcanization, a chemical of theformula where M is a metal, n is a number equal to the valence of themetal, and R and R are non-aromatic hydrocarbon moieties having takentogether a total of at least 1 l carbon atoms.

2. A composition as in claim I in which R and R taken together containat least 14 carbon atoms.

3. A composition as in claim 1 in which R and R taken together containat least 18 carbon atoms.

4. A composition as in claim 1 in which at least one of R, R has atleast eight carbon atoms.

5. A composition as in claim 1 in which one of R, R is a cycloalkylgroup and the other is alkyl of at least eight carbon atoms.

6. A composition as in claim 1 in which at least one of R, R has atleast 12 carbon atoms.

7. A composition as in claim 1 in which R and R are alkyl groups havingup to 30 carbon atoms.

8. A composition as in claim 1 in which R is a long chain alkyl grouphaving at least eight carbon atoms and R is a shorter chain alkyl grouphaving from three to six carbon atoms.

9. A composition as in claim 8 in which R has at least 12 carbon atoms.

10. A composition as in claim 8 in which R has up to 20 carbon atoms.

11. A composition as in claim 1 in which M is zinc and n is 2.

12. A composition as in claim 1 in which R is dodecyl and R isisopropyl.

13. A composition as in claim 1 in which M is zinc, n is 2, R is dodecyland R is isopropyl.

14. The composition of claim 1 in unvulcanized form.

15, The composition of claim 1 in vulcanized form.

16. A method of making a vulcanizate comprising subjecting tovulcanizing conditions the composition of claim 1.

17. A composition as in claim 1 in which the highly unsaturated rubber(B) is SBR.

18. A composition as in claim 1 in which the highly unsaturated rubber(B) is NBR.

2. A composition as in claim 1 in which R and R'' taken together containat least 14 carbon atoms.
 3. A composition as in claim 1 in which R andR'' taken together contain at least 18 carbon atoms.
 4. A composition asin claim 1 in which at least one of R, R'' has at least eight carbonatoms.
 5. A composition as in claim 1 in which one of R, R'' is acycloalkyl group and the other is alkyl of at least eight carbon atoms.6. A composition as in claim 1 in which at least one of R, R'' has atleast 12 carbon atoms.
 7. A composition as in claim 1 in which R and R''are alkyl groups having up to 30 carbon atoms.
 8. A composition as inclaim 1 in which R is a long chain alkyl group having at least eightcarbon atoms and R'' is a shorter chain alkyl group having from three tosix carbon atoms.
 9. A composition as in claim 8 in which R has at least12 carbon atoms.
 10. A composition as in claim 8 in which R has up to 20carbon atoms.
 11. A composition as in claim 1 in which M is zinc and nis
 2. 12. A composition as in claim 1 in which R is dodecyl and R'' isisopropyl.
 13. A composition as in claim 1 in which M is zinc, n is 2, Ris dodecyl and R'' is isopropyl.
 14. The composition of claim 1 inunvulcanized form.
 15. The composition of claim 1 in vulcanized form.16. A method of making a vulcanizate comprising subjecting tovulcanizing conditions the composition of claim
 1. 17. A composition asin claim 1 in which the highly unsaturated rubber (B) is SBR.
 18. Acomposition as in claim 1 in which the highly unsaturated rubber (B) isNBR.
 19. A composition as in claim 1 in which the highly unsaturatedrubber is cis-polybutadiene rubber.
 20. A composition as in claim 1 inwhich the highly unsaturated rubber is polychloroprene rubber.
 21. Acomposition as in claim 1 in which the highly unsaturated rubber ispolyisoprene rubber.
 22. A composition as in claim 1 in which thenon-conjugated diene in (A) is dicyclopentadiene.
 23. A composition asin claim 1 in which the non-conjugated diene in (A) is5-ethylidene-2-norbornene.